ZnO particles with an average size of about 5nm were prepared via a sol-gel chemical route and the silane coupling agent, (3-glycidyloxypropyl)- trimethoxysilane (GPTS), was adopted to enhance the dispersion of the ZnO nanoparticles in ethyl glycol (EG) solution. A ZnO surface potential as high as 66mV was observed and a sedimentation test showed that the ZnO precursor solution remains transparent for sixmonths of storage, elucidating the success of surface modification on ZnO nanoparticles. The ZnO thin films were then prepared by spin coating the precursor solution on a Si wafer and annealing treatments at temperatures up to 500 °C were performed for subsequent preparation of ZnO thin film transistors (TFTs). Microstructure characterization revealed that the coalescence of ZnO nanoparticles occurs at temperatures as low as 200 °C to result in a highly uniform, nearly pore-free layer. However, annealing at higher temperatures was required to remove organic residues in the ZnO layer for satisfactory device performance. The 500 °C-annealed ZnO TFT sample exhibited the best electrical properties with on/offratio = 105, threshold voltage = 17.1V and mobility (μ) = 0.104cm2V- 1s- 1.